Improvement in compressed-air engines



W.O.TUR1 iBULL. I 4

AIR ENGINE. No. 27,938.- Patented Aprv 17, 1860.

UNITED STATES- PATENT OFFICE.

w. o. TURNBULL, or BALTIMORE, MARYLAND.

IMPROVEMENT IN COMPRESSED-AIR ENGINES.

Specification forming part of Letters Patent No. 27,938, dated April 17, 1860.

To all whom, it may concern:

Be it known thatL-W. C.-TURNBULL, of the city and county of- Baltimore, and State of Maryland, have invented certain new-and useful lmprovements in the'Gonstruction of Compressed-Air Engines; and I do hereby'de clare that the following is a fulhclear, and exact description of the construction and operation of the same,-referen'ce being had to the accompanying drawings, in which- Figure 1 represents aperspective view from below of a truck and a compressed-air engine attached to it. Fig. 2 represents a longitudinal'vertical section through said air-engine. Figs. 3 and 4 represent detached views, hereinafter to be referred to.

,I am aware that an air-eng ne hasbeen described which was to be propelled by compressed air that was carried by the engine in suitable air-reservoirs connected therewith; but such engines from some fatal defect have never become practical or even used, and I do not know that anything further than mere theorizing has been done in this'line.

I have proven by actual experiment to'niy own' satisfaction that an air-engine for street railroads more particularly can be propelled economically for several miles with the compressed air, which the car or engine can-carry with it in suitable compartments, from which it is supplied to the cylinders; but itis' necessary to the economical 'use of this compressed air so carried that it should be admitted to the cylinders in regular or unifornr volumes, while the body of the-compressed air is constantly diminishing in power by every stroke of the engine. To effect this object, I use a out-off, which is operated by the pressure of the air in the reservoir oncompartinents, so that as the air expands or be comes less powerful a greater quantity shall be admitted to the cylinders, and thus make up. in quantity what the air has lost in density or power. \Yorking compressed air from a reservoir which is not being constantly re:

plenished, but constantly exhausting, is an,

entirely difterent thing from applying steam "by a cntoftwhere steam is constantly being added to the steam-chamber, for in one case th e supply of power diminishes by every stroke of the engine, while with steam it may be increasing notwithstanding the supply that is constantly taken away to work the engine, or

at least kept at a uniform pressure.

My object .is tomake an engine or car that is to be driven by the compressed air, whicn it carries with it, for street-railroad purposes, 'the engine or car to be supplied from reservoirsof compressed air at stations where it is prepared previously, and to have this air automatically supplied to its cylinders in uniform' quantities by'a cut-off that is governed by the pressure of the air in the compartments which earryit, though that pressure he 4 constantly diminishing, and I propose to carry this compressed air in cylinders or in and about the engine or car, as may be most convenient, the space overhead, or under thecar, or under the seats, or between the walls of the car being, if found essential, used for this purpose.

To enable others skilled in the art to make and use my invention, I willproceed to ,describe its construction and operation.

A represents the frame of a car,carriage,

der, the compressed air acting on the piston G in a similar manner as the steam does on the piston of a steam-engine.

. II represents the piston-rod, I the connecting-rod, and-K the crank by 'ineans'of which .one oi the axles C is driven.

L represents a slide-valve or cut-off. It

works within the chest P, and is similar in its construction to a steam-engine valve. It is operated from theeccentric M by means of the lever N; which turns on the fulcrum or shaft (0, the rod 0 of the slide-valve L being secured to the pivoted sleeve I), by means of which the length of'its stroke can be adj usted.

Q represents an air-chest, into which the compressed air passes when it escapes from the air holder or compartment, and which so pplies the air-chest l with a regular volume of I it is under low pressure,

2' same air for each stroke of the pistom the slide-- valve (1 cutting ed the air quicker when the same is under high pressure'and slower when and the compressed as to regulate air in'the air-holder acting. so

the motion of this cut-cit. This operation is performed by the application of the herein-'- aftcr-described devices; which constitute a,

prineipahpart of my invention. The compressed-airescapesfrom theair-h older'throngh;

said spring rests on the .rim 2? of the chest T.

The end of the stem U is pivoted to the lever V, which turns on the fulcrum h, while the longer end of the lever V is connected by means of a link K with the pitman Z, to which the rod to of the cut-off d is pivoted.

W represents a rock-shaft which has its hearings in the journal-boxes. n. It is operated by means of the eccentric X, whose rod Y is pivoted to the arm 0 of said shaft \V. The end oi this shaft is bent in the shape rep-' resented in the drawing-s, and the bent end 12 can freely play within a isp'ivoted to the flat portion of theconnecting-rod Z. v

The operation of this apparatus is as follows: The air-holders E being filled with compressed air, the air-cock S is opened, and the compressed air passes into the chamber T and thence through the pipe Z-into the air chest Q, whence it passes through the ports 1 2 into a. second air-chest P, and thence through the port 3 into the cylinder F. The pressure of the air being veryhigh when the machine is started it causes the diaphragm f to distend and presses the stem [T down ward.

This motion causes the lever V to turn on its fulcrum 71, Figs. 3'and 4, and to slip the swiveln-ut q on the shank p of the rock-shaft \V,-

whereby a proportional long stroke is imparted to the side (Z, which thus cuts elf the air quickly and-admits onlysuch a volume of air into the chest P as is necessary to drive the engine at a certain speed. As th ressure of the air in the air-holder decreases, the'stem U is raised by the action of the spring g and the swivel-nut (1 slides nearer to the line of the axis of the rock-shaft W; and the-stroke of the rod 1 is shortened, which causes the ports 1 and 2 to remain opposite each other for a longer period of time, and thus to pass an equivalent volume of air into the chest I at a low pressure as was admitted before at a high pressure and for a shorter period. This operation continues until the pressure of air in the air-holder is so low .ricdgand, ita'cts.

by the sct-screw'5, and

swivel-nut g, which that the fulcrum of the swivcl'l-nut'q'is iii the elongation-of the axis of when the motion of the slide '(Z'will be alt-o:

getber arrested-and, there.avill-be an unin terrupted communication between the air-' holder and the air-chestRand the 'slidewalvc "L alone admitsnnd' cuts oft the'air, the one it being inactive. v engine the motion of the cut-off L is notvacut-off of a steam-engine, passing the'com'- pressed air alternately through the ports 3 to the front and to the rear of the piston G, and

causing'the'same after each stroke to escape through the exit. orexhaust'port 4.

The tulcrum hot 7 jus'ted so as to adjust the length'ot the arms of said lever. ing devices: .The pink turns in thebody of a slide 1", whichc'an be moved over the brace s and can be secured in any desired position said pin is secnred'to the sleeve t, Whichoan be moved. over the lever V, and canbe secured. thereto by a setserew 6, thusaflording two adj ustmentsone on the brace sand the other on the lever V by which the action of this regulating apparatusfcan be adjusted with the greatest accuracy. The two air-holders E are connected to each other by a pipe u, by which the density of the air'in both holders remains the same. 7 Thus it will be seen that the velocity .of the engine is the same throughout the differ'ent degrees of pressure of the air. bywhich i t is driven, as the air is cut off quicker while under high pressure than when under low pressure, and that this cut-0E is operated by the pressure of the air itself in the air-holder.

A lever can be applied to the air-valves or their rods; sothat the engineer or conductor from his stand on starting his car or engine may let on a greater volume of air than the cut-off would supply.

The air holders or compartments may be instantly filled by connecting them with the mainsupply-reservoirs at the station or end of the route, which reservoirs are kept supplied by steam or other power through an airpump. A pair of cylinders which I have used in my experiments have held a volume of air compressed to three hundred pounds to the square inch, and I see no difiiculty in holding 1 and carrying air at twice that pressure.

It is well known that heat applied to air increasesits expansive properties, and I propose to apply. to my car or engine, should it be found advantageous to do so, a charcoal fire or gas-furnace, by which the air may be heated to increase its expansive properties by passing the air-pipes through, over, or around said the or flame. Other fircsor heat may be used; but the sparks and smoke in a city would be dangerous and annoying.

I have describedthevalves as operated by eccentrics on the axles of the driving-wheels; but of course the air may be let onby'the conductor or engineer with an ordinary start:-

the rock-shaft W,'.

During the operation of the inthe same manner asthe' the lever V can be ad-f This is effected by the followring-bin and worked by hand, when so preferred. v Y

Having thus fully described the nature of my invention, what I claim therein as new and desire to secure by Letters Patent is- The application to compressed-air engines of an expansion cut-01f which is operated by a positive motion, but the stroke of which is regulated automatically by the pressure of the an m the airiholder or reservoir, so as to admit a, volume of air ofa certain density directly to and allow it to expand in the cylinder for each stroke of the piston as is necessary'to drive the engine at a certain speed, substantially in the manner herein described.

W. G. TURNBULL. Witnesses:

WM. H. HAYWARD, J. F. WAGNER. 

